The invention is directed to a process for the production of pure sodium polysulfides directly from the elements sodium and sulfur.
It is known from Gmelin, Handbuch der anorganischen Chemie, 8th edition, Natrium (sodium), pages 466 et seq. as well as the supplementary volumes, issue 1, pages 184 et seq. and issue 3, pages 1049 et seq. that sodium sulfide and sodium polysulfide can be produced according to a large number of processes, e.g., by reaction of sodium salts with sulfur compounds, such as a sulfide or hydrogen sulfide, in aqueous or alcoholic solutions or in the fused condition with elemental sulfur in the presence of carbon or carbides as well as by reduction of sodium sulfate with hydrogen or other gases and sulfurizing the primarily formed sulfide to the desired polysulfide.
It is common to all known processes that there are obtained products more or less greatly contaminated with the reactants, which products must be separated from the impurities, e.g., through dissolving in suitable solvents and filtering. Polysulfides produced in solution likewise are more or less strongly contaminated by foreign salts. To produce solid anhydrous polysulfides, these products must then be subjected to expensive drying procedures, which is also true for the polysulfides obtained in the so-called amalgam process which polysulfides are pure but likewise only in solution.
It is known that the elements sodium and sulfur react extremely vigorously with each other (enthalpy of formation for Na.sub.2 S: .DELTA.H.sub.B =-389.1 kJ/Mole, for the crystalline Na.sub.2 S.sub.4 : .DELTA.H.sub.298.16 .degree.=-412 kJ/mole), so that as yet it has not been possible to industrially employ directly the elements which are obtainable on the market in great purity to produce the polysulfides.
Rather, there have been attempts to dampen the reaction of sodium with sulfur, e.g., by dissolving the sodium in liquid ammonia or by diluting it through mixing with sodium chloride or by covering it under boiling toluene.